Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$72.52	6.672%	$77.3585	$77.36	$77.35	$77.40
Purchase #2	$58.83	4.601%	$61.5368	$61.54	$61.55	$61.50
Purchase #3	$37.78	9.672%	$41.4341	$41.43	$41.45	$41.40
Purchase #4	$108.31	6.128%	$114.9472	$114.95	$114.95	$114.90
Purchase #5	$196.97	9.583%	$215.8456	$215.85	$215.85	$215.80
Purchase #6	$115.85	9.721%	$127.1118	$127.11	$127.10	$127.10
Purchase #7	$67.58	4.505%	$70.6245	$70.62	$70.60	$70.60
7 purchase totals =	$657.84		$708.8585	$708.86	$708.85	$708.70